1. Field Of The Invention
The present invention relates to locking apparatus for downhole packers, and more particularly, to a locking apparatus which prevents premature setting of a packer by longitudinal movement of an actuating mandrel in the packer with respect to the packer elements.
2. Description Of The Prior Art
The use of packers to close off portions of a well bore is well known. Many of these packers are actuated into a set position by manipulation of the tool string. One such packer is the Halliburton Services Champ.RTM. III packer which is a multiple purpose retrievable packer designed for testing, treating and squeezing. The packer is set by turning the tool string to the right and setting down weight. The packer includes elastomeric packer elements which are squeezed outwardly into sealing engagement with the well casing by movement of an actuating mandrel connected to the tool string. Pressure applied below the packer forces hydraulic slips against the casing to prevent the packer from being pumped up the hole. A straight upward pull releases the packer. A similar packer is the Halliburton RTTS (Retrievable Test-Treat-Squeeze) packer.
When either of these packers is run into the well bore, the mandrel is held in the run-in position by interaction of a lug on the mandrel with a J-slot. Such an arrangement works well with normal, relatively undeviated well bores. However, when such packers are used in highly deviated sections of a well bore, dragging forces on the tool string resulting from contact thereof with the well bore may be enough to cause the mandrel to be prematurely actuated in the J-slot so that the packer elements are squeezed out towards their sealing position. When this occurs, the packer elements may be split because of squeezing forces on them or they may be damaged by contact with the well bore.
This damage to the packer elements may not become known until an attempt is made to set the packer, after which it is necessary to remove the tool string and replace the packer elements. Obviously, this can result in significant lost rig time. Therefore, there is a need for an apparatus to prevent such premature setting of packers.